BACKGROUND OF THE INVENTION
[0001] The present invention relates to a rotary developing device comprising a cylindrical
rotary developing unit, a plurality of development members mounted around the periphery
of said rotary developing unit, and a driving means, wherein the rotary developing
unit is driven by the driving means to bring one of the development members to the
developing position facing a photoreceptor and subsequently the transmission of the
driving power to the development member is conducted
[0002] In a conventional multi-color image forming apparatus employing a rotary development
method, a plurality of development members are mounted along the periphery of a rotary
developing unit and the rotary developing unit is driven to sequentially bring the
development members to a developing position so as to carry out the development operation.
For this, a driving means for rotating the rotary developing unit and a driving means
for rotating a development roller or the like built in each development member mounted
on the rotary developing unit are separately provided.
[0003] The rotary developing unit with the aforementioned plurality of development members
is generally cylindrical and is provided around its outer periphery with heavy parts
such as development rollers as developer carriers which are metallic rollers or metallic
shafts covered by elastic material for developing latent images formed on a latent
image carrier such as a photoreceptor. Accordingly, the rotary developing unit has
large moment of inertia.
[0004] In case of a rotary developing unit having four color development members as a general
example for multi-color printing, development is carried out by driving the rotary
developing unit to rotate 90 degrees four times so as to sequentially bring the four
color development members to a position facing the photoreceptor. As arrangements
for retaining the rotary developing unit in the state after the rotary developing
unit is stopped at the developing position where the development operation is conducted,
there are a case of using the retaining force of a motor itself and a case of providing
an engaging member separately.
[0005] As the moment of inertia is large for conducting 90-degree rotation of the rotary
developing unit, the motor as the driving means must produce a large force in proportion
as the moment of inertia. For raising the printing speed, the increase in speed of
conducting the 90-degree rotation is effective. However, as the speed of the 90-degree
rotation is increased, the acceleration during the rotation is increased. Since the
power required for the driving means should be a square of the acceleration relative
to the moment of inertia, the required power must be great.
[0006] The required power for rotating the rotary developing unit produces in turn the contrary
effect on stopping the rotary developing unit. For stopping the rotary developing
unit, the driving means carries out a braking function to reduce the rotational force
of the rotary developing unit. Ideally, the rotational force of the rotary developing
unit is reduced to zero by the braking force just before the rotary developing unit
is stopped.
[0007] In the electrophotographic technology, a stepping motor is generally used for driving
the rotary developing unit because it can achieve the short-time acceleration and
achieve the higher positioning accuracy with relatively simple control and a DC brushless
motor is generally used for driving the development members because it can provide
high torque efficiency and it never breaks down due to load fluctuation.
[0008] When a DC brushless motor, not a stepping motor, is used for driving the rotary developing
unit, an encoder is fixed to the output shaft of the motor because the DC brushless
motor has poor positioning accuracy. The rotation angle of the motor is determined
from signals from the encoder. According to this information, the rotation angle of
the rotary developing unit is controlled. In addition, the DC brush less motor has
poor acceleration. Accordingly, since a time lag is generated in transmitting and
receiving of the signals from the encoder, it is impossible to rotate the rotary developing
unit at high speed.
[0009] The feedback control according to the signals from the encoder increases the load
on a CPU as a controller. The increase in load on the CPU restricts the entire operation
of the apparatus. From the above reasons, the use of a stepping motor is common for
driving the rotary developing unit. However, even stepping motor has problems such
as vibration, noise, and smaller flexibility for load fluctuation. Because of the
smaller flexibility, the motor should break down to stop the operation at its worst.
In addition, stepping motor is expensive as compared to other motors such as DC brushless
motor relative to the same torque.
[0010] On the other hand, nowadays there are some types employing a stepping motor, not
a DC brushless motor, for driving the development members. One of triggers for the
employment of stepping motor is that decrease in cost of stepping motors has been
achieved as compared to other motors. Moreover, its shorter acceleration/deceleration
time has come to the fore as a merit. For achieving the increase in printing speed,
it is desired to shorten the acceleration time for raising the speed of a development
roller to the steady state velocity as well as the time for switching colors according
to the rotation of the rotary developing unit.
[0011] For actually switching between the rotary unit driving action and the development
member driving action, the rotary developing unit is driven to rotate 90 degrees four
times so as to sequentially bring development cartridges to a position facing the
photoreceptor and a development input gear of the development cartridge, brought to
the aforementioned position, is meshed with a development member driving gear, whereby
the transmission of the driving power to the development roller is conducted. During
this, the pitch circles of the gears meet so that their tooth tops may collide with
each other in some cases. In the event of collision, the driving means may develop
trouble (may stop due to breakdown of the motor) and may produce image defects due
to vibration generated by the collision.
[0012] Due to backlash and deflection existing in a driving-side gear train and deformation
of the rotary developing unit itself, rotational force may remain. The remaining rotational
force is transmitted as vibration to the entire device through the driving means when
the rotary developing unit is stopped. The vibration may be transmitted to an exposure
means or a latent image carrier. In this case, the vibration produces registration
error during formation of latent image. The vibration may be transmitted to a transferring
section. In this case, the vibration produces transferring error.
[0013] Further, when a driving means for rotating the development roller starts to operate
just after the rotary developing unit is stopped, uneven rotation of the driving means
or vibration generated in the driving means is transmitted to the entire device. Similar
to the vibration generated at the stop of the rotary developing unit, the vibration
after the stop of the rotary developing unit produces image defects such as registration
error.
[0014] If the aforementioned two driving means are of different kinds or having rots of
different sizes, the driving means have different rotation and vibration characteristics.
Even when the driving means have substantially the same vibration characteristics,
since these are disposed in different places, these are influenced by the characteristics
of the respective places when subjected to vibration. Vibrations generated by different
vibration sources may be composed of different components. These vibrations may not
damp each other and may be sometimes superposed to be synthesized i.e. amplified,
thus producing image defects such as errors in longer period.
[0015] When a stepping motor is used for driving the rotary developing unit and a DC brushless
motor is used for driving the development roller, the stepping motor is in the stopped
state during the action of driving the development roller (this action will be sometimes
referred to as "the development member driving action"). The stopped state means that
the motor is energized with a minute electric current to retain the rotor at a predetermined
position. In case of having an external locking mechanism for retaining the rotary
developing unit at a predetermined position, it is possible to cancel the retention
of the rotor. However, once the retention of the rotor is cancelled, the position
of the rotor should be unstable. In this case, the position of the first exciting
phase for the next action for driving the development roller is not certain, causing
position error and thus reducing the rotational accuracy of the rotary developing
unit. Consequently, the retention of the rotor is indispensable to maintain the rotational
accuracy of the rotary developing unit.
[0016] However, the retention of the rotor requires the consumption of electric power. Since
the motor is energized but the motor itself does not rotate, the energy applied to
the motor becomes heat energy, increasing the temperature. The increase in temperature
leads to drop in torque.
[0017] When stepping motors are used for driving the rotary developing unit and for driving
the development roller, respectively, drivers for controlling the stepping motors
and timers for controlling the drivers are required, respectively. Besides the aforesaid
timers, another timer of a longer cycle is also required for retaining the stepping
motor for driving the rotary developing unit in the stopped state during the development
member driving action.
[0018] In the rotary developing unit, the amounts of developers in the respective developer
cartridges vary according to the development operation so that the load balance of
the cylinder varies delicately. The variation in load balance increases the moment
of inertia in the rotary developing unit, thereby increasing the torque required to
the stepping motor. Accordingly, it is required to periodically match the motor torque
in a very short cycle during the action of driving the rotary developing unit (this
action will be sometimes referred to as "the rotary unit driving action"). This is
because the timer of a very short cycle is used. If the timer of a very short cycle
is used also for retaining the stopped state, the CPU should be overdriven and thus
restrict the other operation. Addition of such drivers and timers makes the substrate
structure complex and also makes the control, including the control of the CPU, complex.
It should be understood that the addition of such drivers and timers increases superposed
driving time, leading to increase in electrical consumption.
SUMMARY OF THE INVENTION
[0019] It is an object of the present invention to quickly damp vibration generated according
to the rotation of a rotary developing unit and the rotation of development rollers.
It is another object of the present invention to avoid a collision of tooth tops between
gears which may occur due to switching between the rotary unit driving action and
the development member driving action and damp the impact generated by the collision,
thereby reducing vibration and transferring error. It is still another object of the
present invention to shorten the time for switching between the rotary unit driving
action and development member driving action and prevent the generation of vibration,
thereby reducing image defects and image deterioration resulting from registration
error.
[0020] For this, according to the present invention, a rotary developing device comprises:
a cylindrical rotary developing unit, a plurality of development members mounted around
the periphery of said rotary developing unit, a rotary developing unit driving section
for driving said rotary developing unit by a driving means, and a driving power transmitting
section for transmitting the driving power by said driving means to said development
members at a developing position, wherein said rotary developing unit is driven by
said driving means to bring one of said development members to the developing position
facing a photoreceptor and subsequently the transmission of the driving power to said
development member is conducted, and is characterized in that, in said driving power
transmitting section, the driving direction of said development members is set to
be the same as the driving direction of said rotary developing unit and that said
driving power transmitting section is provided with a clutch for coupling/uncoupling
a gear train.
[0021] It is preferable that said driving power transmitting section has a supporting means
for supporting a shaft of a gear to be meshed with a development input gear to transmit
the driving power to the development member in such a manner that the shaft can swing
along a radial line extending from the center of said rotary developing unit and that
said driving power transmitting section is provided with a clutch for coupling/uncoupling
a gear train and, in said driving power transmitting section, the driving direction
of said development members is set to be the same as the driving direction of said
rotary developing unit. Further, it is preferable that said supporting means is positioned
downstream of said driving means in the rotational direction of said rotary developing
unit.
[0022] It is preferable that said clutch is a one-way clutch which is disposed between a
gear to be meshed with the development input gear of said rotary developing unit and
the driving shaft of said gear in said driving power transmitting section.
[0023] It is preferable that, as said driving means, a common driving means is provided
for driving the rotary developing unit and driving the development members and said
rotary developing unit driving section includes a clutch for coupling and uncoupling
a gear train relative to an input gear of the rotary developing unit. Further, it
is preferable that said rotary developing unit has a locking mechanism for retaining
the stopped state during the suspension of the driving of the rotary developing unit
and, in said driving means, reverse pulse is applied to coincide with the direction
of vibration of a motor pinion just after the development member driving action is
finished. Furthermore, it is preferable that said common driving means is set such
that the rotational direction thereof for driving said rotary developing unit and
the rotational direction thereof for driving said development member are opposite
to each other.
[0024] According to the present invention, a rotary developing device comprises: a cylindrical
rotary developing unit, a plurality of development members mounted around the periphery
of said rotary developing unit, a rotary developing unit driving section for driving
said rotary developing unit by a driving means, a driving power transmitting section
for transmitting the driving power by said driving means to said development members
at a developing position, a one-way clutch which is arranged between said driving
means and the driving power transmitting section to couple/uncouple a gear train,
and a retaining means for retaining said rotary developing unit at a developing position,
wherein said rotary developing unit is driven by said driving means to bring one of
said development members to the developing position facing a photoreceptor and subsequently
the transmission of the driving power to said development member is conducted, and
is characterized in that, in said driving power transmitting section, the driving
direction of said development members is set to be the same as the driving direction
of said rotary developing unit, and that said retaining means retains said rotary
developing unit at said developing position during the development member driving
action and said driving means is energized to rotate in reverse at the end of the
development member driving action and subsequently the retention of the rotary developing
unit is cancelled.
[0025] It is preferable that said one-way clutch is disposed between a gear to be meshed
with the development input gear of said rotary developing unit and the driving shaft
of said gear in said driving power transmitting section and that, as said driving
means, a common driving means is provided for driving the rotary developing unit and
driving the development members and said rotary developing unit driving section includes
a clutch for coupling and uncoupling a gear train relative to an input gear of the
rotary developing unit. Further, it is preferable that said retaining means comprises
a locking mechanism having a claw portion for stopping the rotation of said rotary
developing unit and an operating portion for engaging/disengaging the claw portion.
[0026] It is preferable that, as said driving means, driving means are separately provided
for driving said development members and for driving said rotary developing unit and
the driving means for driving said rotary developing unit also functions as said retaining
means and that, when the driving means drives in reverse at the end of said development
member driving action, reverse pulse is applied to coincide with the direction of
vibration of a motor pinion just after the development member driving action is finished.
It is preferable that said driving means is a stepping motor. Further, it is preferable
that, in the driving power transmitting section, the development member driving action
is conducted via a development input gear mounted to the frame of said rotary developing
unit.
[0027] Still other objects and advantages of the invention will in part be obvious and will
in part be apparent from the specification.
[0028] The invention accordingly comprises the features of construction, combinations of
elements, and arrangement of parts which will be exemplified in the construction hereinafter
set forth, and the scope of the invention will be indicated in the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029]
Fig. 1 is an illustration showing an embodiment of a rotary developing device according
to the present invention;
Fig. 2 is a side view of a gear train section of the rotary developing device shown
in Fig. 1;
Fig. 3 is an illustration showing another embodiment of a rotary developing device
according to the present invention;
Figs. 4(A), 4(B) are side views each showing a gear train section of the rotary developing
device shown in Fig. 3;
Fig. 5 is an illustration showing a rotary developing unit of a dual motor driven
type with an arrangement for preventing the damage of tooth tops at a driving power
transmitting section relative to a development input gear;
Fig. 6 is an illustration showing a rotary developing unit of a single motor driven
type with an arrangement for preventing the damage of tooth tops at a driving power
transmitting section relative to a development input gear;
Fig. 7 is a side view showing the power transmitting section as shown in Fig. 5 and
Fig. 6;
Figs. 8(A), 8(B) are illustrations for explaining the retreating action in the event
of collision between tooth tops;
Figs. 9(A)-9(G) are illustrations showing various tooth configurations designed for
reducing the impact and damage generated in the collision between tooth tops;
Fig. 10 is an illustration showing an arrangement with a rotary unit locking mechanism;
Fig. 11 is a diagram for explaining the operational sequence of a motor, a clutch
and a locking solenoid;
Figs. 12(A), 12(B) are diagrams for explaining the operational sequence for switching
between the rotary unit driving action and the development member driving action and
for locking/unlocking the rotary developing unit;
Fig. 13 is a graph for explaining the motor driving sequence for changing color; and
Fig. 14 is a graph for explaining the behavior of a motor pinion when the development
member driving action is finished.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0030] Hereinafter, embodiments of the present invention will be described with reference
to the drawings. Fig. 1 is an illustration showing an embodiment of a rotary developing
device according to the present invention, Fig. 2 is a side view of a gear train section
of the rotary developing device. In these drawings, numeral 1 designates a rotary
developing unit, 2 designates a rotary input gear, 3 designates each development cartridge,
4 designates a development roller gear, 5 designates each idle gear, 6 designates
a development input gear, 10 designates a photoreceptor, 11 designates a development
member driving gear, 12 designates a motor pinion, 13 designates a development member
driving motor, 14 designates a motor pinion, and 15 designates a rotary unit driving
motor.
[0031] In Fig. 1, the rotary developing unit 1 has a substantially cylindrical shape and
is provided around its periphery with a plurality of development cartridges 3 to develop
latent images formed on a latent image carrier such as a photoreceptor 10. The rotary
developing unit 1 is a structural example of a four-color developing unit with development
cartridges 3 for four colors of yellow Y, cyan C, magenta M, and black K. The rotary
developing unit 1 has a rotary input gear 2 coaxially disposed with the rotation axis
thereof and is driven to rotate by a rotary unit driving motor 15 as a driving means
through a gear train of connecting a motor pinion 14 of the rotary unit driving motor
15 and the rotary input gear 2. The rotary developing unit 1 is driven to rotate 90
degrees four times so as to sequentially bring the development cartridges 3 for four
colors to a position facing the photoreceptor 10, respectively, thereby carrying out
development.
[0032] Each development cartridge 3 comprises a development roller as a developer carrier
which is a metallic roller or a metallic shaft covered by an elastic member. The development
roller is driven by a development member driving motor 13 as a driving means through
a gear train composed of a motor pinion 12 of the development member driving motor
13, a development member driving gear 11, a development input gear 6, an idle gear
5, and a development roller gear 4. Thus, the development operation is carried out.
During this development operation, the rotary developing unit 1 is retained in the
stopped state by the rotary unit driving motor 15.
[0033] The rotary developing unit 1 is mounted to a body frame 20 as well as the development
member driving motor 13 and the rotary unit driving motor 15 as shown in the side
view of Fig. 2 and has a rotary shaft 7 which is rotatably supported by bearings.
As for the gear train for driving each development cartridge 3, the development input
gear 6 for each development cartridge 3 is mounted to a rotary frame 8 while the idle
gear 5, meshed with the development input gear 6, and the development roller gear
4 are mounted to each development cartridge 3. The development cartridges 3 are individually
detachable. The idle gear 5 of each development cartridge 3 is meshed with the corresponding
development input gear 6 fixed to the rotary frame 8 when the development cartridge
3 is installed.
[0034] Each development input gear 6 is fixed to the rotary frame 8 in such a manner that
the development input gear 6 can be meshed with the development member driving gear
11 fixed to the body frame 20, while it can also be meshed with the idle gear 5 of
the corresponding development cartridge 3. Therefore, even when the development cartridges
3 are replaced, variation in quality of the development cartridges 3, if any, does
not affect the mesh between the development member driving gear 11 and the development
input gear 6. After a development cartridge 3 is installed, the mesh between the development
member driving gear 11 and the idle gear 5 remains until the replacement of the development
cartridge 3. On the other hand, the mesh between the development input gear 6 and
the development member driving gear 11 is repeatedly achieved and cancelled according
to the rotary unit driving action and the development member driving action. The tooth
tops of the development input gears 6 and the development member driving gear 11 are
therefore easily damaged so that their lives are shortened. According to the structure
of the present invention, however, the prolongation of the lives of driving power
transferring parts such as the development member driving gear 11 and the development
input gears 6 can be achieved.
[0035] The transmission of driving power is conducted on the path of rotational contact
of the rotary developing unit 1 and the pitch circles of the gears (the development
input gear 6 and the development member driving gear 11) meet so that their tooth
tops may collide with each other in some cases. In the event of collision, the driving
means may develop trouble (may stop due to power swing of the motor), easily damaging
the tooth tops and shortening their lives. For this, by employing a one-way clutch
in the development member driving gear 11, as some tooth tops intend to collide with
each other during the rotational action, the one-way clutch can run idle, thereby
avoiding such a collision and preventing the driving means from developing trouble.
[0036] The development member driving gear 11 employing the one-way clutch idles in a direction
of rotating the rotary developing unit 1 by the rotary unit driving motor 15 as the
driving means. On the other hand, during the development operation, the rotary unit
driving motor 15 is held in the stopped state and the development member driving gear
11 is rotated by the development member driving motor 13 as the driving means in the
reverse direction of the idling direction of the development member driving gear 11
to drive the development input gear 6. In this case, therefore, the rotational direction
of the rotary input gear 2 and the rotational direction of the development input gear
6 are the same.
[0037] One-way clutch is much advantageous than electromagnetic clutch. For example, unlike
electromagnetic clutches, the coupling and uncoupling can be automatically conducted
without necessity of conduction so that no control is required and no electrical component
such as a controller for controlling the ON/OFF is required. The one-way clutch needs
no electricity, thereby achieving power saving and needs no time for conducting the
coupling and uncoupling. That is, the switching is conducted at very high speed. Further,
the one-way clutch can be enough small to be built in the gear and yet transmit a
large torque so that it has high degree of freedom of design.
[0038] Fig. 3 is an illustration showing another embodiment of a rotary developing device
employing a one-way clutch and Figs. 4(A), 4(B) are side views each showing a gear
train section of the rotary developing device shown in Fig. 3. Though separate motors
(two motors) are employed as driving means for the rotary unit driving action and
the development member driving action, respectively in the aforementioned embodiment,
a single motor is employed as a common driving means for the rotary unit driving action
and the development member driving action in this embodiment of Fig. 3. Figs. 4(A)
and 4(B) are side views showing examples of different arrangements of a one-way clutch
in a development member driving gear, respectively.
[0039] In Fig. 3, a development member driving motor 13 drives a motor pinion 12 to rotate
in the clockwise direction, thereby conducting the rotary unit driving action and
drives the motor pinion 12 to rotate in the counter-clockwise direction, thereby conducting
the development member driving action. To make the single motor capable of conducting
the rotary unit driving action and the development member driving action, a development
member driving gear 11 employing a one-way clutch is arranged between the motor pinion
12 and a development input gear 6, while a gear 16 with an electromagnetic clutch
(hereinafter, referred to as the electromagnetic clutch gear 16) is arranged between
the motor pinion 12 and a rotary unit driving gear 17.
[0040] When the motor pinion 12 is driven to rotate in the clockwise direction for conducting
the rotary unit driving action, the electromagnetic clutch gear 16 is set into its
coupled state to drive the rotary input gear 2 and the one-way clutch idles to separate
the power transmission to the developer cartridges 3. When the motor pinion 12 is
driven to rotate in the counter-clockwise direction for conducting the development
member driving action, the electromagnetic clutch gear 16 is set into its uncoupled
state to separate the power transmission to the rotary input gear 2 and the motor
pinion 12 drives one of the development input gears 6 via the development member driving
gear 11.
[0041] The electromagnetic clutch gear 16 which is meshed with the rotary unit driving gear
17 for conducting the rotary unit driving action and the development member driving
gear 11 which is meshed with one of the development input gears 6 for conducting the
development member driving action are mounted to a body frame 20 as shown in the side
views of Figs. 4(A), 4(B). The development member driving gear 11 employing the one-way
clutch (hereinafter, referred to as the one-way clutch gear 11) is arranged at a side
where it can be meshed with the motor pinion 12 or at a side where it can be meshed
with one of the development input gears 6. The arrangement in which the one-way clutch
gear 11 is arranged to be meshed with the motor pinion 12 is shown in Fig. 4(A), while
the arrangement in which the one-way clutch gear 11 is arranged to be meshed with
one of the development input gears 6, i.e. the one-way clutch is fitted between a
gear to be meshed with one of the development input gears 6 and the shaft of the gear
is shown in Fig. 4(B).
[0042] In the arrangement shown in Fig. 4(A) in which the one-way clutch gear 11 is arranged
to be meshed with the motor pinion 12, when a gear 11a, which is a counter part of
the one-way clutch gear 11 and is meshable with the development input gear 6, collides
with the development input gear 6, the gear 11a, the shaft, and the ratchet gear fitted
in the one-way clutch gear 11 idle. On the other hand, in the arrangement shown in
Fig. 4(B) in which the one-way clutch gear 11 is arranged to be meshed with one of
the development input gear 6, when the one-way clutch gear 11 collides with the development
input gear 6, only the gear 11 which is meshable with the development input gear 6
idles. Therefore, the arrangement shown in Fig. 4(A) operates with a heavy load, making
collision relief between tooth tops difficult, in comparison to the arrangement shown
in Fig. 4(B) according to the position of the one-way clutch gear 11. Therefore, the
arrangement shown in Fig. 4(B) has an advantage over the arrangement shown in Fig.
4(A).
[0043] Instead of the one-way clutch, a single tumbler mechanism may be employed in the
development member driving gear 11. In this case, the development member driving gear
11 may be supported such that its shaft can swing in a direction of a radial line
extending from the center of the rotary developing unit 1 by the single tumbler mechanism
so that the development member driving gear 11 can be neatly meshed with one of development
input gears 6 for transmitting driving power. Hereinafter, embodiments employing a
single tumbler mechanism will be described. Fig. 5 is an illustration showing a rotary
developing unit of a dual motor driven type with an arrangement for preventing the
damage of tooth tops at a driving power transmitting section relative to a development
input gear, Fig. 6 is an illustration showing a rotary developing unit of a single
motor driven type with an arrangement for preventing the damage of tooth tops at a
driving power transmitting section relative to a development input gear, Fig. 7 is
a side view showing a power transmitting section as shown in Fig. 5 and Fig. 6, and
Figs. 8(A), 8(B) are illustrations for explaining the retreating action in the event
of collision between tooth tops.
[0044] In Fig. 5, the development member driving gear 11 is supported by a single tumbler
mechanism not a gear with clutch mechanism. It should be understood that an electromagnetic
clutch gear and a one-way clutch gear which can idle in the rotary unit driving direction
may be employed. Other structure is the same as that in the embodiment shown in Fig.
1. As one of developer cartridges 3 is brought to a position facing the photoreceptor
10 by 90-degree rotation of the rotary developing unit 1, the development input gear
6 is meshed with the development member driving gear 11, thereby conducting the transmission
of driving power. When tooth tops of the development input gear 6 and the development
member driving gear 11 collide with each other, the shaft of the development member
driving gear 11 is shifted along the radial line extending from the center of the
rotary developing unit 1 by a single tumbler mechanism 21 in such a manner that the
development member driving gear 11 retreats, whereby the development member driving
gear 11 can be neatly meshed with the development input gear 6 according to the rotation
of the development member driving gear 11. The single tumbler mechanism 21 is a supporting
means for supporting the shaft of the development member driving gear 11 as a part
of the power transmitting portion such that the shaft can swing in the direction of
the radial line extending from the center of the rotary developing unit 1.
[0045] Since the rotary unit driving action and the development member driving action are
alternately repeated and are never conducted at the same time, only a single motor
is enough for the rotary developing unit, instead of two motors of a development member
driving motor 13 and a rotary unit driving motor 15 in the embodiment shown in Fig.
5. An embodiment in which a single motor is used is shown in Fig. 6. In the rotary
developing unit of a single motor driven type as shown in Fig. 6, a rotary input gear
2 is meshed with a rotary unit driving gear 17 and is driven by a motor pinion 12
through an electromagnetic clutch gear 16 and the rotary unit driving gear 17. In
this case, for conducting the rotary unit driving action, a development member driving
motor 13 drives a motor pinion 12 to rotate in the clockwise direction and the electromagnetic
clutch gear 16 is set to its coupled state. For conducting the development member
driving action, the development member driving motor 13 drives the motor pinion 12
to rotate in the counter-clockwise direction while the electromagnetic clutch gear
16 is set to its uncoupled state. In this case, the development input gear 6 is driven
to rotate in the same direction of the driving direction of the rotary developing
unit 1 by the development member driving gear 11.
[0046] By employing a common motor as driving means, vibration produced by one of the actions
can be reduced by vibration produced by the other action. Immediately after the rotary
unit driving action is finished, the same motor is driven to rotate in the reverse
direction for starting the development member driving action, thereby quickly damping
vibration produced by the rotation of the rotary developing unit and thus preventing
deterioration of image quality due to unevenness and/or registration error resulting
from such vibration.
[0047] In the gear train for the rotary unit driving action, the rotary input gear 2 is
always meshed with the motor pinion 12 via the rotary unit driving gear 17 and the
electromagnetic clutch gear 16 both during the rotary unit driving action and during
the development member driving action, so the engagement and disengagement action
of teeth is not conducted. Therefore, the problem of collision between tooth tops
is basically not caused. In the gear train for the development member driving action,
however, the problem may be caused. When the developer cartridges 3 are moved to the
position facing the photoreceptor 10 one by one, some tooth tops of the development
member driving gear 11 may collide with some tooth tops of the development input gear
6, causing damage of tooth tops and producing vibration and thus deteriorating the
image quality. This is true both in the dual motor driven type and the single motor
driven type.
[0048] The single tumbler mechanism 21 is a relief mechanism for damping the impact generated
in the collision and reducing the damage of tooth tops. The mechanism is shown in
a side view of Fig. 7. The shaft of the development member driving gear 11 is supported
at its one end to a body frame 20 in such a manner that the shaft can swing in a direction
of a radial line extending from the center of the rotary developing unit 1 by the
single tumbler mechanism 21. In addition, the development member driving gear 11 is
biased by a spring toward the center of the rotary developing unit 1 so that the development
member driving gear 11 can be meshed with one of the development input gears 6.
[0049] As shown in Fig. 5 and Fig. 6, one of the development rollers can be brought into
contact with the photoreceptor 10 on a radial line extending from the center of the
rotary developing unit 1 and the development member driving gear 11 is biased and
supported to swing by the single tumbler mechanism 21 such that the development member
driving gear 11 can be meshed with one of the development input gears 6 on a radial
line extending from the center of the rotary developing unit 1. According to this
structure, even when impact is generated by collision between tooth tops of the development
member driving gear 11 and the development input gear 6, the development member driving
gear 11 is shifted against the spring force not to affect the contact portion between
the development roller and the photoreceptor 10.
[0050] When the development input gear 6 is moved to a position where it can be meshed with
the development member driving gear 11 according to the rotary unit driving action
and collides with some tooth tops, the development member driving gear 11 is shifted
in a direction away from the rotary developing unit 1 along a radial line extending
from the center of the rotary developing unit 1 as a result of the function of the
single tumbler mechanism 21 as shown in Fig. 8(A) and Fig. 8(B). Then, tooth tops
of the development input gear 6 slide in valleys of the teeth of the development member
driving gear 11 while the development input gear 6 moves to the exactly meshable position
according to the rotary unit driving action, whereby the development input gear 6
can be neatly meshed with the development member driving gear 11. Alternatively, in
case that the collision between tooth tops can not cancelled even when the development
input gear 6 reaches the exactly meshable position, the development input gear 6 can
be neatly meshed with the development member driving gear 11 according to the movement
of the tooth tops of the gears at the beginning of the development member driving
action, that is, when the development member driving motor 13 is started to rotate
for the development member driving action.
[0051] In a case that the development member driving gear 11 supported by the single tumbler
mechanism 21 is positioned upstream of the motor pinion 12 in the rotating direction
of the rotary developing unit as shown in Fig. 8(A) and Fig. 8(B), when the development
member driving gear 11 swings, the development member driving gear 11 rotates in a
direction attacking the development input gear 6 to be meshed with the development
member driving gear 11 because of the coupling with the motor pinion 12. In a case
that the development member driving gear 11 is positioned downstream of the motor
pinion 12 in the rotating direction of the rotary developing unit i.e. an inverse
arrangement from that of the illustrated case, when the development member driving
gear 11 swings, the development member driving gear 11 rotates in a direction away
from the development input gear 6 to be meshed with the development member driving
gear 11 because of the coupling with the motor pinion 12. Accordingly, the later case
should be advantageous to allow smooth reciprocating motion of the single tumbler
mechanism 21.
[0052] In case of the development member driving gear 11 employing a one-way clutch as shown
in Fig. 1 and Fig. 3, there is a condition that the rotary input gear 2 and the development
input gear 6 rotate in the same direction. In case of single motor driven type as
shown in Fig. 3 and Fig. 6, both the normal rotation and the reverse rotation are
switched and driven by one motor. In an arrangement shown in Fig. 3 which is of a
single motor driven type and in which a one-way clutch is employed in the development
member driving gear 11, the rotary input gear 2 and the development input gear 6 are
driven to rotate in the same direction. If the development member driving gear employs
an electromagnetic clutch not a one-way clutch and two motors are used for driving,
the driving directions of the rotary input gear and the development input gear can
be selected, respectively.
[0053] Figs. 9(A)-9(G) are illustrations showing various tooth configurations designed for
reducing the impact and damage generated in the collision between tooth tops. In each
figure, a dashed line indicates a pitch circle, a thin line indicates a tip circle,
and arrows indicate the rotational directions of a driving-side gear and a driven-side
gear, respectively. Fig. 9(A) shows details of a tooth configuration of a normal involute
gear, and driving- and driven-side gears. In comparison with the involute tooth shown
in Fig. 9(A), various tooth configurations are designed for reducing the impact and
damage generated in the collision between tooth tops. As an example, Fig. 9(B) shows
gears in which a tip portion of each tooth is cut on a side not the contact side of
the tooth. The cutting is limited to a position between the pitch circle and the tip
circle. Fig. 9(C) shows high-tooth gears having high teeth of which rate is 30%. Fig.
9(D) shows high-tooth gears having high teeth of which tops are rounded. According
to Japanese Industrial Standard, the involute tooth consists of curves so that it
is believed that the height limit is the position of a point where two curves meet
with each other at the top. A gear with too deep bottom should be "undercut configuration"
in view of mold construction so that there is a limit of mold releasing.
[0054] In comparison with Fig. 9(E) which is a perspective view showing the normal involute
tooth, Fig. 9(F) and Fig. 9(G) show tooth configurations designed for reducing the
impact and damage generated in the collision be between tooth tops, in which Fig.
9(F) is a perspective view of a helical gear and Fig. 9(G) is a perspective view of
a tooth having inclined surfaces in the longitudinal direction of the tooth.
[0055] The development input gear 6 moves to the position to be meshed with the one-way
clutch gear 11 according to the rotary unit driving action and the rotary developing
unit stops at the developing position. If some tooth tops still collide with each
other in this state, the gears are neatly meshed with each other according to the
movement of the tooth tops of the gears when the development member driving motor
13 is started to rotate for the development member driving action. In this case, vibration
is generated due to impact when the gears are meshed so that the actual development
is started before the vibration does not die out completely. By employing gears having
any one of the aforementioned tooth configurations, the gears can be smoothly meshed
with each other until the rotary developing unit stops at the developing positions,
whereby the actual development can be started without vibration as mentioned.
[0056] Fig. 10 is an illustration showing an arrangement with a rotary unit locking mechanism,
in which numeral 41 designates a receiving concavity, 42 designates a solenoid, 43
designates a locking lever convexity, and 44 designates a spring. For example, as
shown in Fig. 10, a rotary unit locking mechanism for stopping and retaining the rotary
developing unit 1 at a desired position comprises receiving concavities 41 formed
in the outer periphery of the rotary developing unit 1 and a locking lever convexity
43. By pivotally moving the locking lever convexity 43 to be fitted (engaged) in one
of the receiving concavities 41, the rotary developing unit 1 is stopped at a desired
position. The locking lever convexity 43 is operated to pivot about a pivotal axis
by a solenoid 42 as a switching device and is locked at a position where the development
roller of one of the developer cartridges faces the photoreceptor 10.
[0057] In the locking mechanism shown in Fig. 10, the spring 44 applies a force for retaining
the locked state to the engaging portion, thereby preventing the lever from moving
due to its weight in a direction canceling the engagement. Since the development roller
and the photoreceptor 10 rotate and abut on each other, a reaction force acting to
rotate the rotary developing unit 1 is generated to and a force acting to cancel the
engagement is generated as an effect of the reaction. Therefore, the spring 44 is
set to give a force enough for retaining the engaged state against the force acting
to cancel the engagement. In response to this, the solenoid 42 is set to provide a
force of extending the spring 44 against the spring force in order to cancel the engagement.
[0058] It should be noted that the aforementioned arrangement is just a major example and
that the same is true of a case with a single motor. Of cause, there are various locking
mechanisms. For instance, a reverse operation clutch is disposed which can be meshed
with a gear of a gear train (driving-side gear train) rotating the rotary developing
unit such that the reverse operation clutch is engaged with the gear so as to hold
the rotary developing unit at a predetermined developing position when not energized
and is disengaged from the gear to allow the rotation of the rotary developing unit
for changing color when energized.
[0059] Fig. 11 is a diagram for explaining the operational sequence of the motor, the clutch
and the solenoid for the rotary unit locking mechanism (hereinafter, referred to as
the locking solenoid), Figs. 12(A), 12(B) are diagrams for explaining the operational
sequence for switching between the rotary unit driving action and the development
member driving action and for locking/unlocking the rotary developing unit, Fig. 13
is a graph for explaining the motor driving sequence for changing color, and Fig.
14 is a graph for explaining the behavior of the motor pinion when the development
member driving action is finished.
[0060] In the operational sequence of the motor, the clutch and the locking solenoid, the
rotary unit driving (RT driving) action and the development member driving action
are alternatively repeated with holding intervals. The motor is driven along a velocity
curve composed of an acceleration (speedup) period, a constant speed period, and a
deceleration (slowdown) period in each action. On the other hand, the electromagnetic
clutch is ON over the period of the rotary unit driving action to transmit power from
the driving motor to the rotary input gear and is OFF over a period from one holding
interval and the next holding interval through the development member driving action.
In response to the ON of the electromagnetic clutch, the locking solenoid is ON over
the period of the rotary unit driving action to cancel the engagement for retaining
the rotary developing unit. The solenoid is OFF over the period of the development
member driving action to stop the rotation of the rotary developing unit.
[0061] In Fig. 12(A), the rotary unit driving motor is designated by "Mr" and the development
member driving motor is designated by "Md". In the arrangement shown in Fig. 1 and
Fig. 2 having both these motors, the development member driving motor "Md" is driven
to rotate in reverse at the end 'a' of the development driving action. In Fig. 12(B),
the driving motor which is common for the rotary unit driving action and the development
member driving action is designated by "Mc". In the arrangement shown in Fig. 3 and
Figs. 4(A), 4(B), the driving motor "Mc" is driven to rotate in reverse, i.e. rotate
in the same direction as that for the rotary unit driving action, at the end 'a' of
the development driving action. On the other hand, the electromagnetic clutch "CI"
is ON (in the coupled state) over the period of the rotary unit driving action to
transmit the power from the driving motor "Mc" to the rotary input gear and is OFF
over the period from one holding interval to the next holding interval through the
development member driving action. In response to the ON of the electromagnetic clutch
"CI", the locking solenoid "SI" is ON over the period of the rotary unit driving action
to cancel the engagement for retaining the rotary developing unit. The locking solenoid
"SI" is OFF over the period of the development member driving action to stop the rotation
of the rotary developing unit.
[0062] Residual stress at the engaging portion between the receiving concavity 41 and the
locking lever convexity 43 generates a force (reaction force) in a direction opposite
to the direction of the development member driving action. Though the shaft of the
gear normally rotates and the gear portion idles because of the function of the one-way
clutch when the motor rotate in reverse, the gear portion is also rotated in reverse
together with the motor shaft due to the reaction force, thereby removing the residual
stress at the engaging portion and thus conducting the printing action without problems
such as image defects.
[0063] The timing of rotating the motor in reverse is controlled to synchronize the reverse
driving direction of the motor with the direction of vibration which is generated
on the output shaft of the driving means due to the development member driving action.
When the reverse driving direction of the motor is opposite to the direction of vibration
at the beginning of reverse rotation, the torque exceeds the capacity of the motor
so that the motor may be out of order. Even though the motor can operate, the vibration
of the motor should be so large to produce image defects at image forming portions.
By driving the motor at a timing enabling the synchronization of the reverse driving
direction of the motor with the direction of the vibration generated on the output
shaft of the driving means due to the development member driving action, such problem
can be solved.
[0064] Since the repulsion of the residual stress acts on the engaging portion at the beginning
of the reverse rotation, the motor should be subjected to zero load or minus load
(braking force). By conducting the reverse rotation with electric current smaller
than the normal current (current during the development member driving action), the
vibration is suppressed, thereby preventing the production of image defects. The use
of a stepping motor is preferable because the detailed control of pulse and current
is enabled to achieve the best operation, thereby achieving the formation of high
quality images.
[0065] When a pulse motor is used as the rotary unit driving motor, motor pulse is generated
to correspond to its velocity curve as shown in Fig. 13. Fig. 13 plots frequency of
the motor pulse as the ordinate and time as the abscissa. In case that the rotary
unit driving action and the development member driving action are both conducted by
a single motor, since the pinion vibrates just after the development member driving
action is finished as shown in Fig. 14, reverse pulse is applied to coincide with
the direction of the vibration. Because of the reverse pulse, the residual stress
generated on the engaging portion can be removed by the reaction force of driving
power, thereby preventing the failure of cancellation of the engagement and reducing
the vibration generated due to the cancellation of the engagement.
[0066] It should be understood that the present invention is not limited to the aforementioned
embodiments and various changes and modifications may be made. For example, though
the gear, employing a one-way clutch and to be meshed with the development input gear
of the rotary developing unit, is mounted to the body frame in the aforementioned
embodiments, the one-way clutch gear may be arranged at any place from an idle gear
or a motor gear to a gear directly driving a roller of a developer cartridge. Though
a one-way clutch gear is employed as a driving-side gear to be meshed with development
input gears in the aforementioned embodiments, an electromagnetic clutch gear may
be employed or a combination of a single tumbler mechanism 21 and a one-way clutch
gear may be employed instead of the one-way clutch gear.
[0067] As apparent from the above description, the present invention can provide a rotary
developing device comprising a cylindrical rotary developing unit, a plurality of
development members mounted around the periphery of the rotary developing unit, a
rotary developing unit driving section for driving the rotary developing unit by a
driving means, and a driving power transmitting section for transmitting the driving
power by the driving means to the development members at a developing position, wherein
the rotary developing unit is driven by the driving means to bring one of the development
members to the developing position facing a photoreceptor and subsequently the transmission
of the driving power to the development member is conducted. In the driving power
transmitting section, the driving direction of the development members is set to be
the same as the driving direction of the rotary developing unit and a simple additional
structure employing an electromagnetic clutch or a one-way clutch is applied to the
driving power transmitting section, thereby avoiding a collision of tooth tops between
gears at the driving power transmitting section, damping the impact generated by a
collision, and reducing vibration and damage of tooth tops. Therefore, it can prevent
the production of image defects due to registration error.
[0068] Because the driving power transmitting section employs a clutch capable of coupling
and uncoupling the gear train, the mesh between a development member driving gear
and a development input gear can be smoothly conducted, thereby avoiding a collision
of tooth tops between the gears, damping the impact generated by a collision, reducing
vibration and noise, and reducing damage of tooth tops.
[0069] Further, the driving power transmitting section has a supporting means for supporting
the shaft of a gear to be meshed with the development input gear to transmit the driving
power in such a manner that the shaft can swing along a radial line extending from
the center of the rotary developing unit, thereby avoiding a collision of tooth tops
between gears which occurs at the driving power transmitting section when switching
from the rotary unit driving action to the development member driving action, damping
the impact generated by a collision, and reducing vibration and damage of tooth tops.
Therefore, it can prevent the production of image defects due to registration error.
[0070] The driving power transmitting section employs a clutch capable of coupling and uncoupling
the gear train, the driving direction of the development member is set to be the same
as the driving direction of the rotary developing unit, and the supporting means is
positioned downstream of the driving means in the rotational direction of the rotary
developing unit, whereby the mesh between the development member driving gear and
the development input gear can be smoothly conducted, thereby further avoiding a collision
of tooth tops between the gears, damping the impact generated by a collision, reducing
vibration and noise, and reducing damage of tooth tops.
[0071] The clutch is a one-way clutch and is disposed between a gear to be meshed with the
development input gear of the rotary developing unit and the driving shaft of the
gear in the driving power transmitting section, thereby enabling the automatic switching
between coupling and uncoupling and thus achieving power saving. Further, the one-way
clutch needs no time for conducting the coupling and uncoupling, thereby shortening
the switching time. Furthermore, the one-way clutch can provide high degree of freedom
of design as compared to an electromagnetic clutch, achieve power saving and simplification
of control, and curb the rise in temperature, thus improving the driving reliability.
[0072] As for the driving means, a common driving means is provided for driving the rotary
developing unit and driving the development members. A rotary developing unit driving
section includes a clutch for coupling and uncoupling a gear train relative to an
input gear of the rotary developing unit. The rotary developing unit has a locking
mechanism for retaining the stopped state during the suspension of the rotary developing
unit. In the driving means, reverse pulse is applied to coincide with the direction
of vibration of a motor pinion just after the development member driving action is
finished. The common driving means is set such that the rotation for driving the rotary
developing unit is opposite to the rotation for driving the development member. Therefore,
the coupling/uncoupling of either clutch can be done by rotation of the driving means
(motor) in either direction so that the rotary unit driving action and the development
member driving action can be conducted by the single motor. Further, the common driving
means can retain the rotary developing unit in the stopped state during the development
member driving action, yet smoothly cancel the stopped state, and quickly damp vibration,
thereby forming high quality images without image defects such as unevenness and registration
error resulting from such vibration.
[0073] According to the present invention, a rotary developing device comprising a cylindrical
rotary developing unit, a plurality of development members mounted around the periphery
of the rotary developing unit, a rotary developing unit driving section for driving
the rotary developing unit by a driving means, a driving power transmitting section
for transmitting the driving power by the driving means to the development members
at a developing position, a one-way clutch which is arranged between the driving means
and the driving power transmitting section to connect/disconnect a gear train, and
a retaining means for retaining the rotary developing unit at a developing position,
wherein the rotary developing unit is driven by the driving means to bring one of
the development members to the developing position facing a photoreceptor and subsequently
the transmission of the driving power to the development member is conducted. In the
driving power transmitting section, the driving direction of the development members
is set to be the same as the driving direction of the rotary developing unit. The
retaining means retains the rotary developing unit at a developing position during
the development member driving action and drives the driving means in reverse at the
end of the development member driving action to allow the movement of the rotary developing
unit. Therefore, the locking/unlocking can be smoothly conducted by a simple structure
without vibration, thereby shortening the time for switching between the rotary unit
driving action and development member driving action so as to achieve a large increase
in speed of forming images, and forming high quality images without image defects
such as unevenness and registration error resulting from such vibration.
[0074] The one-way clutch is disposed between a gear to be meshed with the development input
gear of the rotary developing unit and the driving shaft of the gear in the driving
power transmitting section. As for the driving means, a common driving means is provided
for driving the rotary developing unit and driving the development members. The rotary
developing unit driving section includes a clutch for coupling and uncoupling a gear
train relative to an input gear of the rotary developing unit. The retaining means
comprises a locking mechanism having a claw portion for stopping the rotation of the
rotary developing unit and an operating portion for engaging/disengaging the claw
portion. The switching between the rotary unit driving action and the development
member driving action can be conducted by the normal rotation and reverse rotation
of a single motor and further the switching time can be shortened, thereby achieving
a large increase in speed and power saving. Further, the one-way clutch can provide
high degree of freedom of design as compared to an electromagnetic clutch, achieve
power saving and simplification of control, and curb the rise in temperature, thus
improving the driving reliability.
[0075] As for the driving means, driving means are separately provided for driving the development
members and for driving the rotary developing unit. The driving means for driving
the rotary developing unit is also used as the retaining means. When the driving means
drives in reverse at the end of the development member driving action, reverse pulse
is applied to coincide with the direction of vibration of a motor pinion just after
the development member driving action is finished. Therefore, the locking/unlocking
can be smoothly conducted without vibration and the time for switching between the
rotary unit driving action and development member driving action can be shortened,
thereby achieving a large increase in speed of forming images, and forming high quality
images without image defects such as unevenness and registration error resulting from
such vibration.
[0076] By employing a stepping motor as the driving means, the positioning accuracy is increased
and the switching action at a high speed with high accuracy is achieved. In the driving
power transmitting section, the development input gear is mounted to the frame of
the rotary developing unit so that the development member driving action is conducted
via the development input gear. Therefore, even if a development member is replaced,
no influence is exerted on the meshing part.
[0077] According to the present invention, as discussed in the above, the switching between
the rotary unit driving action and the development member driving action can be smoothly
conducted to shorten the time, thereby achieving a large increase in speed of multi-color
development. The coupling/uncoupling is automatically conducted, the switching between
the rotary unit driving action and the development member driving action can be conducted
by the normal rotation and reverse rotation of a single motor, thereby improving the
driving reliability and achieving the simplification of substrate, reduction in controlling
load, and power saving. Further, high quality images can be formed without image defects
such as unevenness and registration error resulting from such vibration.
1. A rotary developing device comprising: a cylindrical rotary developing unit, a plurality
of development members mounted around the periphery of said rotary developing unit,
a rotary developing unit driving section for driving said rotary developing unit by
a driving means, and a driving power transmitting section for transmitting the driving
power by said driving means to said development members at a developing position,
wherein said rotary developing unit is driven by said driving means to bring one of
said development members to the developing position facing a photoreceptor and subsequently
the transmission of the driving power to said development member is conducted, said
rotary developing device being characterized in that,
in said driving power transmitting section, the driving direction of said development
members is set to be the same as the driving direction of said rotary developing unit.
2. A rotary developing device as claimed in claim 1, wherein said driving power transmitting
section is provided with a clutch for coupling/uncoupling a gear train.
3. A rotary developing device comprising: a cylindrical rotary developing unit, a plurality
of development members mounted around the periphery of said rotary developing unit,
a rotary developing unit driving section for driving said rotary developing unit by
a driving means, and a driving power transmitting section for transmitting the driving
power to said development members at a developing position by said driving means,
wherein said rotary developing unit is driven by said driving means to bring one of
said development members to the developing position facing a photoreceptor and subsequently
the transmission of the driving power to said development member is conducted, said
rotary developing device being characterized in that,
said driving power transmitting section has a supporting means for supporting a
shaft of a gear to be meshed with a development input gear to transmit the driving
power to the development member in such a manner that the shaft can swing along a
radial line extending from the center of said rotary developing unit.
4. A rotary developing device as claimed in claim 3, wherein said driving power transmitting
section is provided with a clutch for coupling/uncoupling a gear train.
5. A rotary developing device as claimed in claim 3 or 4, wherein in said driving power
transmitting section, the driving direction of said development members is set to
be the same as the driving direction of said rotary developing unit.
6. A rotary developing device as claimed in claim 3, wherein said supporting means is
positioned downstream of said driving means in the rotational direction of said rotary
developing unit.
7. A rotary developing device as claimed in any one of claims 1-6, wherein said clutch
is a one-way clutch.
8. A rotary developing device as claimed in claim 7, wherein said one-way clutch is disposed
between a gear to be meshed with the development input gear of said rotary developing
unit and the driving shaft of said gear in said driving power transmitting section.
9. A rotary developing device as claimed in any one of claims 1-8, wherein as said driving
means, a common driving means is provided for driving the rotary developing unit and
driving the development members and said rotary developing unit driving section includes
a clutch for coupling and uncoupling a gear train relative to an input gear of the
rotary developing unit.
10. A rotary developing device as claimed in claim 9, wherein said rotary developing unit
has a locking mechanism for retaining the stopped state during the suspension of the
driving of the rotary developing unit.
11. A rotary developing device as claimed in claim 9, wherein, in said driving means,
reverse pulse is applied to coincide with the direction of vibration of a motor pinion
just after the development member driving action is finished.
12. A rotary developing device as claimed in claim 9, wherein said common driving means
is set such that the rotational direction thereof for driving said rotary developing
unit and the rotational direction thereof for driving said development member are
opposite to each other.
13. A rotary developing device comprising: a cylindrical rotary developing unit, a plurality
of development members mounted around the periphery of said rotary developing unit,
a rotary developing unit driving section for driving said rotary developing unit by
a driving means, a driving power transmitting section for transmitting the driving
power by said driving means to said development members at a developing position,
a one-way clutch which is arranged between said driving means and the driving power
transmitting section to couple/uncouple a gear train, and a retaining means for retaining
said rotary developing unit at a developing position, wherein said rotary developing
unit is driven by said driving means to bring one of said development members to the
developing position facing a photoreceptor and subsequently the transmission of the
driving power to said development member is conducted, said rotary developing device
being characterized in that,
in said driving power transmitting section, the driving direction of said development
members is set to be the same as the driving direction of said rotary developing unit,
and that
said retaining means retains said rotary developing unit at said developing position
during the development member driving action and said driving means is energized to
rotate in reverse at the end of the development member driving action and subsequently
the retention of said rotary developing unit is cancelled.
14. A rotary developing device as claimed in claim 13, wherein said one-way clutch is
disposed between a gear to be meshed with the development input gear of said rotary
developing unit and the driving shaft of said gear in said driving power transmitting
section.
15. A rotary developing device as claimed in any one of claims 13-14, wherein as said
driving means, a common driving means is provided for driving the rotary developing
unit and driving the development members and said rotary developing unit driving section
includes a clutch for coupling and uncoupling a gear train relative to an input gear
of the rotary developing unit.
16. A rotary developing device as claimed in any one of claims 13-15, wherein said retaining
means comprises a locking mechanism having a claw portion for stopping the rotation
of said rotary developing unit and an operating portion for engaging/disengaging the
claw portion.
17. A rotary developing device as claimed in claim 13, wherein as said driving means,
driving means are separately provided for driving said development members and for
driving said rotary developing unit and the driving means for driving said rotary
developing unit also functions as said retaining means.
18. A rotary developing device as claimed in any one of claims 13-16, wherein when the
driving means drives in reverse at the end of said development member driving action,
reverse pulse is applied to coincide with the direction of vibration of a motor pinion
just after the development member driving action is finished.
19. A rotary developing device as claimed in any one of claims 1-18, wherein said driving
means is a stepping motor.
20. A rotary developing device as claimed in any one of claims 1-19, wherein in the driving
power transmitting section, the development member driving action is conducted via
a development input gear mounted to the frame of said rotary developing unit.